Previous studies of two histamine H2-receptor antagonists, cimetidine and ranitidine, suggest that they increase blood alcohol concentrations by decreasing the first pass metabolism of ethanol. Ranitidine has also been shown to accelerate gastric emptying of ethanol. While some studies have confirmed that ranitidine can increase blood alcohol levels, the effect was too small to be clinically significant. These studies did not include social drinkers, who tend to repetitively consume small amounts of ethanol. Arora and colleagues studied the impact of ranitidine on the blood alcohol levels of social drinkers.

Men with a history of consuming fewer than five standard drinks per week were enrolled in the study. Social drinking was simulated with four small drinks, 150 mg per kg of ethanol, alternating with potato chips, given every 45 minutes. Breath analysis for ethanol was performed 15 minutes after the drink was consumed and then every five minutes until the next drink. After this initial test, the patients were given ranitidine in a dosage of 150 mg twice a day for one week. The consumption of small drinks and breath analysis were repeated.

Blood alcohol levels rose after the patients took ranitidine for one week. In seven of the nine participants, blood alcohol levels while ranitidine was being taken exceeded 25 mg per dL (5.4 mmol per L), a level at which judgment and finely tuned skills are impaired. The high levels persisted for a longer time during ranitidine use than they had done before the medication was used.

The authors conclude that social drinking during ranitidine therapy is associated with an increase in blood alcohol levels. The levels rise to the point that judgment and the psychomotor skills needed to operate a motor vehicle may be impaired. Social drinkers should be made aware of this potential and warned about the effect ranitidine may have on their blood alcohol levels.